Treatment

There are no clinical studies of the treatment of inhalational anthrax in humans. Accordingly, much remains unknown about the best antibiotic or treatment regimens. Given the rapid course of symptomatic inhalational anthrax, early antibiotic administration is essential.

A delay of antibiotic treatment for patients with anthrax infection even by hours may substantially lessen chances for survival. Given the difficulty in achieving rapid microbiological diagnosis of anthrax, all persons with fever or evidence of systemic disease in an area where anthrax cases are occurring should be treated for anthrax until the disease is excluded as a possibility.

Most naturally occurring anthrax strains are sensitive to penicillin, and penicillin historically has been the preferred therapy for the treatment of anthrax. Penicillin is approved by the FDA for this purpose, as is doxycycline. Although the treatment of anthrax infection with ciprofloxacin has not been studied in humans, animal models suggest excellent efficacy. Reports have been published of a B anthracis vaccine strain that has been engineered by Russian scientists to resist tetracycline (doxycycline) and penicillin classes of antibiotics1.

The following are the recommendations of the Working Group on Civilian Defense in cases in which there is clinically evident anthrax infection in the setting of mass casualties or for post exposure prophylaxis:

Adults: Ciprofloxacin 500 mg by mouth every 12 hours for 60 days. If it is determined that amoxicillin or doxycycline are effective against that strain of B anthracis, they can be used instead, in doses of amoxicillin 500 mg every 8 hours for 60 days or doxycycline 100 mg by mouth every 12 hours for 60 days.

Children: Ciprofloxacin, 20 mg/kg to 30 mg/kg per day by mouth divided into 2 daily doses, not to exceed 1 gram per day. If it is determined that amoxicillin is effective against that strain of B anthracis, then it can be used instead in doses of:

Weight 20 kg or greater, 50 mg by mouth every 8 hours for 60 days.

Weight less than 20 kg, 40 mg/kg divided into 3 does to be taken every 8 hours for 60 days. Doxycycline is not recommended for children.

Decontamination

The greatest risk to human health following an intentional aerosolization of anthrax spores occurs during the period in which anthrax spores remain airborne, called the primary aerosolization.The duration for which spores remain airborne and the distance spores travel before they become noninfectious or fall to the ground is dependent on weather conditions and the properties of the aerosol method. It is the feeling of the Working Group on Civilian Biodefense that under circumstances of maximum survival and persistence, the aerosol would likely be fully dispersed within hours to 1 day at most,well before the first symptomatic cases would be seen.

The risk that anthrax spores might pose to public health after the period of primary aerosolization can be inferred from the Sverdlovsk experience. At Sverdlovsk, new cases of inhalational anthrax developed as late as 43 days following the presumed date of release, but none occurred during the months and years afterward. While it is impossible to state with certainty that 'secondary aerosolization' (becoming infected from spores that had already settled in the environment) did not occur, it appears unlikely. Few efforts were made to decontaminate the environment after the accident and only 47,000 of the city's 1 million people were vaccinated. The occurrence of cases over time would suggest that one could account for virtually all patients having been within the area of the accident at the time of primary aerosolization. If secondary aerosolization had been important, new cases almost certainly would have continued for a period well beyond the observed 43 days.

Infection Control

There is no data to suggest patient-to-patient transmission of anthrax occurs2. Standard barrier isolation precautions are recommended for hospitalized patients with all forms of anthrax infection, but the use of specially designed masks, etc. is not indicated. There appears to be no need to immunize or provide prophylactic treatment to patient contacts unless it is determined that they too were exposed to the aerosol at the time of the attack.

For those humans or animals that die of the disease, proper burial or cremation is important. Serious consideration should be given to cremation. Embalming of bodies could be associated with special risks to the embalmers. If autopsies are performed, all related instruments and materials should be sterilized by autoclave or incinerated.

Michael E. Pezim, MD in association with the MediResource Clinical Team